Control systems for hot cathode vacuum tubes



Jan. 10, 1933.

A. MUTSCHELLER CONTROL SYSTEMS FOR HOT CATHODE VACUUM TUBES Filed Aprill0. 1926 TETE-JRE: .1 7;

2 Sheets-Sheet 1 lNVENTOR ATTORNEY Janf 10, 1933 A. MuTscHELLER1,894,051

CONTROL SYSTEMS FOR HOT CATHODE VACUUM TUBES Filed April l0. 1926 2Sheets-Sheet 2 :F.TTRE; E 4

ATTORNEY 'rss ARTHUR MUTSCHELLEE, F NEW YORK, Iii. Y., ASSGNOR TOVAPPLEB ELECTRIC COMPANY, ENC., A CORPORATIN GF NEW YORK CONTR-OLSYSTEMS FOR EGT CATHDE 'VACUUM TUBES Application led April 10,

My invention relates to control systems for hot cathode vacuum tubes;that is, to systems in which there are one or more valve tubes and oneor more X-ray tubes, all provided with electrically heated cathodes, andin which the discharges through the tubes are controlled quantitativelyby manual regulation of the circuit or circuits used for heating thecathodes. n

More particularly stated, my invention comprehends a system. welladapted for the production of X-rays capable of use in other relations,and in which two or more separate circuits, used for heating filamentsor other electrodes employed as cathodes to be heated, are togethercontrollable practically as a single unit for the purpose ofquantitatively regulating the currents through the respective tubes.

ln Xray systems used in the prior art it has been found advantageous, inusing an X-ray tube energized by a high tension transformer and having aheated cathode, to employ an auto-transformer connected with the lineand energized thereby at the line voltage, and to provide theauto-transformer with taps from which alternating currents of anyrequired voltage may be fed directly to the primary of the high tensiontransformer. lt f has also been found advantageous to place upon thecore of the auto-transformer ank additional winding, separate from theother winding or windings thereof, and to use this additional winding toheat the cathode, usually a lament, of the X-ray tube. This arrangementresulted in an excellent stabilizing eect upon the voltage impressedupon the X-ray tube, and also enabled the operator to vary at will andpractically independent of the current user for heating the filament,the voltage of the main discharge. 'This system is disclosed in myPatent No. 1,481,876, and is often used in connection with an equipmentwhich includes a hot cathode valve tube in either the primary circuitorthe secondary circuit, and also includes an X-ray tube located in thesecondary circuit and provided with a cathode lament and circuit forheating the same.

I have made the discovery that in using LSE LEX

CFI

1926, Serial No. 161,012.

my system as just noted it is practicable to control, practically as asingle unit, any or all of the circuits used for heating the cathodes,and that when the heating circuits are thus controlledas a unit theefficiency of the system is improved, the speed of operation isincreased, the chances for a breakdown are diminished, and many otheradvantages are obtained.

have made the further discovery that in 6oA order to thus unify thecontrol of a number of heating circuits for the purpose herecontemplated, the circuits may be interconnected either directly orindirectly, as hereinafter ,more particularly described.

Reference is made to the accompanying drawings forming a part of thisspecifica-tion, and in which like reference characters indicate lilreparts throughout the several iigures.

Figure l is a diagram showing a form of 7o my invention in which twocircuits, used for heating two cathode filaments, are interconnected andthus controllable practically as a unit.

Figure 2 is a diagram of another form of 75 my invention, in which acircuit for heating one filament is in series with the primary of aheating transformer the secondary of which is in series with anotherfilament.

Figure 3 is a diagram of a third form, in which two separate filamentheating circuits are controllable by a single switch common to bothcircuits.

A pair of power leads are shown at 4, 5, and are used for energizing anautotransformer 6, with which they are connected by wires 7, 8, 9, andsliding contact switch l0. The auto-transformer is provided with avariable contact switch ll. rlhe switches 10 and 11 are used, eitherindividually or in co-relation as required, for controlling the outputvoltage of the auto-transformer- A high tension transformer appears atand here employed as the main transformer. It is energized by secondarycurrents e5 from the auto-transformer 6. For this purpose it isconnected with the switch l1 by a wire i3, and also with the wires 8 and9 by a wire let. A switch 12L is employed for opening and closing acircuit through the main 100 transformer, without disturbing thevariable contact switch 11. The main transformer is provided with aprimary winding 12b and two secondary windings 15 and 16.

5 A vacuum valve tube appears at 17, and is provided with a valve anode18 and a cathode 19, the latter having the form of a filament adapted tobe heated.

An X-ray tube is shown at 20, and is provided as usual with an anode 21serving as a target, and with a cathode 22 in the form of a filamentadapted to be heated.

A small transformer 23 is used to supply current for heating the cathode19 of the valve tube 17. The secondary winding of the transformer isshown at 24, and by wires 25 and 26 is connected with the cathode 19. Awire 27 connects the cathode 19 with the secondary winding 15 of themain transformer, anda wire 28'extendsfrom the secondary winding 16 rofthe main transformer to the anode 18'of the valve tube. A wire 29 isconnected with the secondary winding 16 and with the cathode 22, andfrom the secw 2londary winding 15 and a wire 30 extends t0 the anode 21of the X-ray tube.

A wire 31 is connected with the wire 29 and with the cathode 22. Wires32 and 33 are connected with the wire 31. The wire 32 39leads to theprimary 23" of the transformer 23, and from this primary av wire 34leads to a rheostat`35. The auto-transformer 6 is provided with twosecondaries 37 and 38,

Vwhich are independent of all other windings. 39?'The winding 37 isconnected with the wire 36. The windings 37 and 38 are connectedtogether and also connected with a wire 39. This wire leads to avariable switch 40, to which the wire 33 also leads.

A wire 41 leads from the secondary 38 to a rheostat 42, and from thelatter a wire 43 leads to a ground connection 44. A wire 45 leads fromthe ground connection 44 and wire 43 to the cathode 22 of the X-ray tube20.

The main transformer 12 is energized by currents from theauto-transformer 6. The vacuum valve tube 17 and the X-ray tube 2O areenergized from the secondary circuit of the main transformer.

The heating of the cathode 19 is accomplished by secondary currents fromthe transformer 23, which is energized by currents from the secondary37, and the cathode 22 is heated directly by currents from the second-55"ary 38. Hence the two secondaries 37 and 38 supply all the currentused for heating the two cathodes.

The rheostat controls the transformer 23, and hence in a general wayregulates the' U9 volume of current supplied to the cathode 19.

The rheostat 42 regulates directly the supply 0f current to the cathode22. However, the

rheostats 35 and 42 are not adjusted very often. They are set right` atthe start, in

05 order to properly apportion the relative amount of current suppliedto the respective cathodes 19 and 22, or in other words, to balance theheating currents relatively to each other, and this done, the rheostats35 and 42 usually require no further attention, at least F until somesubstantial change is made in the wiring.

The switch 40 acts somewhat differently. It not only controls thetransformer 23 and thus indirectly controls the heating current suppliedto the cathode 19, but it also controls directly t-he current forheating the cathode 22. In other words the switch 40 is Common to bothsecondaries 37 and 38, and also to both cathodes 19 and 22. Hence if thetwo rheostats 35 and 42 are properly adjusted at the start, the switch40 alone is adequate to take care of any and all changes requiredthereafter from time to time in the current supplied to the cathodes 19and 22. This means, of course, that the number of milliamperes passingthrough the X-ray tube and used for the production .of X-rays can bevaried within wide limits by merely actuating the single switch 40.

The circuit used for heating the cathode 19 may be traced as follows:Secondary windings 37 and 38 considered as in parallel with each other,wire 39, switch 40 to wire 33, whence the circuit divides; one branchbeing continued as wire 32, primary 23a wire 34, rheostat 35 and wire36, back to secondaries 37 and 38; the other branch being continued fromwire 33 to wire 31, cathode 22, and

thence back by wires 45 and 43 (grounded at 44), rheostat 42 and wire 41to secondary windings 38 and 37.

In the form of my invention shown in Figure 2, the auto-transformer 6 isprovided with a secondary winding 46, and a wire 47 extends from thiswinding to the cathode 19 of the valve tube 17. A wire 48, which isprovided with a ground connection 49, leads from the cathode 19 to avariable switch 50, and from this switch a wire 51 leads to the primarywinding 23n of the transformer 23. A wire 52 leads from the primarywinding 23a to the secondary winding 46 of the autot-ransformer 6. Awire 53 is connected with the cathode 22 of the X-ray tube 20 to thesecondary winding 24 of the transformer 23. A wire 54 leads from thecathode 22 to a variable switch 55, and from the latter a wire 56 leadsto the secondary winding 24.

The cathode 19 of the valve tube 17 is heated directly by currentsinduced in the secondary winding 46, and these same currents euergizethe primary winding 23EL of the transformer 23.

A circuit through the parts just mentioned may be traced as follows:secondary winding 46, wire 47. cathode 19, wire 48 with its groundconnection 49 to switch 50, wire 51, primary winding 23n of transformer23, and

wire 52 back to secondary winding 46. A circuit through the cathode 22may be traced as follows: secondary winding 2-1, wire 53, cathode 22,wire 54, switch 55 and wire 56, back to secondary winding 24C.

The switch 55 is used merely to so adjust the circuit just traced as toapportion the current through the cathode 22 relatively to the currentthrough the cathode 19. This done, practically once for all, the switch50 alone is used for regulating, from time to time as required, thecurrents used for heating both cathodes 22 and 19. When the operatormoves the variable switch 50 in one direction of its travel, bothcathodes 22 and 19 are rendered hotter; and when the switch 50 isshifted in the opposite direction, the two cathodes are rendered lesshot.

1n the form shown in Figure 3 there are some differences as to detail.

A wire 57 is connected with the secondary winding 46, and leadstherefrom to the cathode 22 of the X-ray tube. From this cathode a wire58 leads to a variable switch 59, and thence a wire 60 leads to a doubleswitch 61. From this switch a wire 62 leads back to the secondarywinding 46.

A wire 68 leads from the switch 61 to the primary winding 23EL of thetransformer 23, and from the switch 61 another wire 64 extends to thelead 5. The wire 58 is provided with a ground connection 65. From thelead 4 a wire 66 extends to the primary winding 28a of the transformer23. From the secondary winding 24 of this transformer a wire 67 leads tothe cathode 19, and from the latter a wire 68 leads back to thesecondary winding 24 of the transformer 23.

The sole use of the switch 59 is in adjusting or apport-ioning thecurrent for heating the cathode 22, relatively to the current forheating the cathode 19; and this adjustment, once made, is permanent.

The double switch 61, however, is used for controlling, practically as asingle unit, all of the circuits employed for heating the two cathodes19 and 22.

The circuit for energizing tie primary of the transformer 23 may betraced as follows: lead 5, wire 64;, right hand portion of double switch61, wire 63, primary winding 23a of transformer 23, and wire 66 to lead4. The secondary circuit of the transformer .3 may be traced as follows:secondary winding 2e, wire 67, cathode 19, and wire 68 back to secondarywinding 2i.

rlhe circuit for heating the cathode 22 of the X-ray tube 20 can betraced as follows: secondary winding 46 of the auto-transformer, wire57, cathode 22, wire 58 with its ground connection 65, switch 59, wire60, left hand portion of double switch 61, and wire 62 back to secondarywinding 4G.

lt will be noted that in operating the double switch 61 the operatorcontrols both cathodes 19 and 22. If at the start the switch 59 isproperly adjusted, the control of the'double switch 61 over bothcathodes is perfect and may be maintained for an indefinite period oftime.

lt will also be noted that by means of my system a single regulator isused to control two vacuum tubes, the filament of one being maintainedat Zero or ground potential and the filament of the other being subjectto the highest potentials attainable in the system during operation.

lt is well lrnown to the artthat an X-ray tube operates at what is knownas the saturation point or Zone while a vacuum tube, commonly utilizedfor rectification purposes, opcrates below this saturation point. Owingto this difference in operating characteristics, when it is desired toalter the discharge current flowing through the X-ray tube the ratio ofheating current supplied to the cathode of the X-ray tube must ofnecessity be greater than that supplied to the vacuum or rectier tube.By the novel arrangement of my control system the heating currentsupplied to the cathode of both discharge devices is simultaneouslyvaried and the current supplied to the X-ray tube is readily varied to agreater extent than that supplied to the other discharge device. rl`hismaintains the correct ratio of heating currents between the twodischarge devices over the entire operating range and compensates forthe diiference in operating characteristics between the two dischargedevices.

I do not limit myself to the precise mechanism shown, as variations maybe made therein without departing from my invention, the scope of whichis commensurate with my claims.

Having thus described my invention, what I claim as new and desire tosecure by Letters Patent is as follows:

1. ln a control system for X-ray tubes, the combination with a pluralityof thermionic discharge devices provided with cathodes to be heated, oneof said discharge devices being an X-ray tube, of a main transformer forsupplying energy to the electrodes of said devices, an auto-transformerconnected to a suitable source of electrical energy provided with aplurality of windings for energizing said main transformer and forsupplying heating current to the cathode of one of said devices, aheating transformer for supplying heating currents to the cathode of theother of said devices, a ground connection for one of said cathodes andmeans for varying the currents for heating the cathode of the X-ray tubeto agreater extent than the currents for heating the cathode of anyother discharge device.

2. In a control system for X-ray tubes, the combination with a pluralityof thermionic discharge devices provided with cathodes to be heated, oneof said discharge devices being an X-ray tube, of a inain transformerfor supplying energy to the electrodes of said devices, anauto-transformer connected to a suitable source of electrical energy forenergizing said inain transformer, an auxiliary Winding carried by saidauto-transformer for supplying heating current to the cathode of one ofsaid discharge devices, a low tension transformer having its primaryWinding connected to said auxiliary winding for supplying heatingcurrent to the cathode of the other of said discharge devices, a groundconnection for the cathode of one of said devices, and regulating meansfor simultaneously varying the current supplied by the auxiliary windingof said auto-transformer and said lov.'v tension transformer to thecathodes of said discharge devices.

Signed at Long Island city, in the county of Queens and State of NewYork, this 23th day of April, 1926.

ARTHUR MUTSGHELLER.

